We are interested in those mechanisms that mediate myofibroblast function under normal and pathological conditions. Myofibroblasts are necessary cells for tissue remodeling and repair. During wound healing myofibroblasts differentiate in response to various cellular signals which results in an increase in their muscle gene expression, extracellular matrix secretion, and contractility. The fact that, under certain circumstances, myofibroblasts persist and continue to secrete extracellular matrix has implicated them in interstitial fibrosis of the lung. In this proposal, we are specifically interested in the role that mechanical stress, i.e. contraction, has in regulating endothelial nitric oxide synthase (eNOS) expression and activity in pulmonary myofibroblasts, and subsequently, how changes in eNOS correlate with myofibroblast apoptosis. Understanding those molecular mechanisms that lead to dissipation of myofibroblasts is essential in rational therapeutic design. Therefore, we propose three specific aims to extend our knowledge regarding the role of contraction in mediating myofibroblast apoptosis via eNOS signaling: 1) we will evaluate how contraction of pulmonary myofibroblasts regulates eNOS expression at the gene, RNA, and protein levels, using primary myofibroblast cell cultures; 2) we will determine how nitric oxide mediates pulmonary myofibroblast apoptosis using various pharmacological donors and selective inhibitors of NOS in primary myofibroblast cell cultures; and 3) we will assess the absence of sarcomeric myosin on bleomycin-induced pulmonary fibrosis in vivo histologically and biochemically using the myosin heavy chain IId null transgenic mouse model. The results from these studies will provide significant advancements in our understanding of the pathogenesis of pulmonary fibrosis and other pulmonary interstitial diseases. Furthermore, over the 3 year funding period, this project will engage numerous undergraduates to independent research, enhancing their learning of scientific principles, giving them an opportunity to make unique contributions to the study of this devastating family of diseases, and stimulating their excitement for careers in biomedical research. Interstitial pulmonary fibrosis is a devastating lung disease that results from excess collagen in lungs as a result of a surplus of, and/or overactive, myofibroblast cells. Since, relatively few drugs are available for the treatment of pulmonary fibrosis, and their effectiveness is minimal at best, a thorough understanding of the mechanisms regulating myofibroblast activity and death is important in designing new, improved therapeutics. The nitric oxide pathway is an ideal place to begin in that this pathway is targeted by numerous pharmaceuticals that have already been evaluated for efficacy and toxicity and are approved for use by the U.S. Food and Drug Administration, potentially eliminating years of clinical testing and saving millions of dollars. [unreadable] [unreadable] [unreadable]